1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to an information storage medium and multi-angle data structures.
2. Description of the Related Art
For example, DVDs are information storage media capable of storing multi-angle data. Multi-angle data is recorded on a DVD using an interleaving method in which data to be recorded is divided into predetermined units and recorded in turns. Information for seeking and reproducing interleaved blocks is recorded in motion picture bit-streams.
FIG. 1 shows a data structure of a conventional DVD. Referring to FIG. 1, a DVD storage area includes a VMG area, wherein title information and title menu information are stored, and a plurality of VTS areas, wherein a plurality of movie files are stored. Generally, the VMG area includes two or three files and each VTS area includes three through twelve files. The VTS area may include information for a title as a reproduction unit and a VOBS as motion picture information. A plurality of titles can be stored in one VTS.
FIG. 2 shows a data structure of the VMG area of FIG. 1. The VMG area includes a VMGI area which stores additional information related to the VMG area, a VOBS area which stores video objects for menu, and a backup area of VMGI. Each area exists as one file, and the VOBS area may be omitted in some cases.
FIG. 3 shows a data structure of the VTS area of FIG. 1. The VTS area includes Video Title Set Information (VTSI), a VOBS as motion picture data for menu picture, a VOBS as motion picture information for video title set, and backup data of VTSI. A VOBS for displaying a menu picture can be included selectively in the VTS area. Each VOBS is subdivided into VOBs and cells as recording units. One VOB comprises a plurality of cells. The smallest recording unit may be referred to as a cell.
In the DVD, each layer is a reproduction unit and a title is provided in a top layer. The title is connected with one or more PGCs. A PGC among the plurality of PGCs to be first reproduced is called Entry PGC. A title may comprise only one PGC, that is, an Entry PGC. A title may comprise a plurality of PGCs. In such a case, where reproduction of one PGC is complete, another PGC among the plurality of PGCs may be selected and reproduced, and information on a reproduction sequence of a PGC may be stored as a command in the DVD. A control of such a reproduction sequence may be referred to as Navigation. The command deciding the reproduction sequence may be stored in a PGCI.
FIG. 4 shows a data structure of a PGC of the DVD. Referring to FIG. 4, the PGC is stored as an information structure such as a PGCI. The PGCI comprises a pre-command which stores a navigation command, a post-command, and a plurality of program information. The pre-command is a command performed before reproduction of a corresponding PGC, and the post-command is a command performed after reproduction of a corresponding PGC. Each program is composed of a plurality of cell information. These cells are connected on a one-to-one basis to cells in a VOB as recording units. Each cell has a cell command performed after reproduction of the cell is completed. The PGCI information describes a PGC as a recording unit hierarchically. The PGCI information has an information structure to connect a cell as a lowest reproduction unit to a cell as a lowest recording unit. In the PGC, a plurality of cells as recording units are interconnected, and the plurality of cells form one angle block.
FIG. 5 shows an example of an angle block comprising a plurality of cells arranged in parallel. Upon reproduction, one cell in the angle block is selected and reproduced. The plurality of cells forming the angle block have the same reproduction time and each cell corresponds to angle data in the angle block, angle data divided into interleaved units (ILVUs) as predetermined units are interleaved with each other and recorded to VOBs and Cells as recording units.
FIG. 6 shows VOBs and Cells as recording units in a case of not including multi-angle data. Referring to FIG. 6, each VOB is stored in a continuous block of a contiguous recording space of the information storage medium. In the case of multi-angle data, as shown in FIG. 7, VOBs, each of which corresponds to angle data, and the Cells, as lower units thereof, are recorded as an interleaved block, in which ILVU units are interleaved. Accordingly, one angle data is not stored within a contiguous recording area, and each angle data is interleaved and recorded in a predetermined order.
FIG. 7 shows an arrangement in which two angle data are interleaved and recorded in order. As shown in FIG. 7, each ILVU should have a same reproduction time. A size of a recording length of data may be changed according to data compressibility. To reproduce interleaved data, jumping of the ILVU data unit is required in both cases where one angle data is reproduced, and where one angle data is changed from another angle data and then reproduced. For example, to reproduce data corresponding to angle 1, it is required to seek and reproduce only ILVU data corresponding to the angle 1. To change to another angle data while angle data is reproduced, jumping to a specific location corresponding to the changed angle data should be performed. At this time, the jumping location is also decided based on the ILVU unit.
Location information for an ILVU unit of a corresponding angle and for another ILVU unit of another angle connected to the corresponding angle is recorded in motion picture bit-streams. As shown in FIG. 8, a VOBS as a motion picture bit-stream has a layered structure, and a lowest layer comprises PCKs (PACKs) such as a NV_PCK, A_PCK, V_PCK, and SP_PCK. The NV_PCK is referred to as a navigation pack, and as shown in FIG. 9, stores location and size information SML_AGL_Cn_DSTA of ILVU data for a maximum of nine angles supported by the DVD. These are information for seeking ILVU data for angle n connected to the ILVU data currently being reproduced. After reproducing the present ILVU data, angle change into a desired angle may be performed using this information to reproduce ILVU data for the desired angle. Such location information of ILVU data is multiplexed and recorded in bit-streams of interleaved and recorded motion picture data.
FIG. 10 illustrates jumping into selected angles, in a reproduction order. Referring to FIG. 10, to perform a seamless change to reproduce motion pictures, where an angle change command from a user is received at a specific location, jumping into ILVU data of the desired angle is generated after the reproduction of present ILUV data, and reproduction of the ILVU data of the desired angle is performed.
A conventional authoring process of the DVD for multi-angle data is described below. First, images taken from various angles are compressed respectively and bit-streams having the same reproduction length are created. The bit-streams are interleaved and each bit-stream includes information capable of referring to different angles so as to allow an angle change in the midst of reproduction.
Information related to interleaving is multiplexed and recorded in a motion picture data stream, and therefore is extracted. Generally, an operation to seek and reproduce an interleaved block belonging to an angle, or to change to and thereafter seek and reproduce an interleaved block corresponding to another angle, is processed through software by a CPU of a reproduction apparatus. This software accesses the interleaved block currently being reproduced, obtains location information on a desired interleaved block to be reproduced, and transfers the obtained location information to a data reading device. Also, compressed and encoded motion picture data is processed in a motion picture de-multiplexer. Accordingly, a process for extracting location information from motion picture data and transferring the location information to the CPU is needed.
Furthermore, where multi-angle data is divided into predetermined units, interleaved, and stored, reproduction location change is continuously required in order to read data successively, as the corresponding data is not recorded successively even in a case where one angle data is reproduced successively. Also, a problem exists in that even though a considerable time for location change may be needed with respect to, for example, optical disks or hard disks, bit-rate of compressed bit-streams to compensate for this time is limited.